A non-invasive method to estimate the size of myocardial infarcts and the effect of therapeutic measures on reduction of infarct size consists of recording 35 electrocardiographic leads from the left anterior chest wall. ST segment elevations and QRS changes are used as indicators of myocardial injury. It is well known that much of the information derived from the 35 ECG leads is redundant. Data reduction procedures are, therefore, being applied to the original lead set of 35 in order to determine a smaller number of leads which contain the same information. A data reduction alogrithm developed by Lux and coworkers is being used. More than 200 sets of precordial maps have become available both from CCU at George Washington University and the MILIS data collection under the direction of Dr. Eugene Braunwald. They are being reviewed in order to eliminate incomplete sets and those with excessive artifacts. The reduction in number of leads should lead to a more practical and useful procedure in the managements of patients with acute infarcts.